It is common practice by railroad industries worldwide to utilize an air braking system on both passenger and freight trains. The air brake system is typically composed of a compressed air source and control valves that are normally located on the locomotives and connected through a series of pipes and hoses to the brake valves and brake actuators on each railroad car. The air supply is carried across the span between coupled railroad cars, referred to herein as the “coupler gap”, through a flexible hose/coupler arrangement 26 and 27 in FIG. 8. The air hose coupler, commonly referred to as the “glad hand”, is susceptible to unintended uncoupling if the air hose assembly hangs down sufficiently such that it strikes objects in the track as the train is in motion. By design, any loss of pressure in the air brake system causes the entire train to automatically go into an emergency brake mode and come to a stop, disrupting normal train operations.
The invention described herein is designed to measure the height of the air hose assembly in the coupler gap area between each pair of coupled railroad cars and to automatically send a warning if the minimum air hose height is found to be below a certain limit above the top of rail, typically 4-5 inches. The invention relies on a “machine vision” system that utilizes a camera and computer interface to acquire images of the coupler gap area continuously through the train. These coupler gap images are analyzed in real time with a computer program that seeks to identify the air hose in each image and measure the minimum height of the air hose relative to the top edge of the rail in the image. The invention functions automatically and unattended by virtue of a computerized control system.
An additional function of the invention is to measure the height of each railroad car coupler above the top edge of the rail (FIG. 3). Freight and passenger railroads enforce limits as to the height variation of the coupler above the top of rail to avoid significant mismatches between mating coupler heights. Significant mismatches between mating coupler heights have been shown to create vertical force moments that can unload a railcar's wheels and cause derailments.
The coupler height measurement functions in tandem with the air hose height measurement system requiring no additional equipment. However, the image analysis software program is modified by the addition of an image analysis module that seeks to find the mating couplers in the coupler gap image and measure the height of each coupler shank mid-point above the top of rail. The coupler height value is then compared to the limits imposed by the railroad and a warning issued if coupler height falls outside of this range.
Historically, manual inspection of parked railroad cars has been used to detect a low hanging air hose. If a low hanging air hose catches debris on the ground and brakes, then an emergency braking sequence is initiated. These emergency braking scenarios cost railroads millions of dollars of lost revenue through down time. Also, if the emergency braking mechanisms were to fail, then a lack of braking pressure in a train causes a dangerous situation.
A brief summary of methods/apparatus for remotely detecting whether a specific object is in a safe position follows below.
Prior art consists of devices designed to detect low hanging air hose assemblies by detecting when such assemblies break one or more laser beams aimed across the railroad track to a receiver on the other side of the track. A monitoring system detects the change in the laser receiver output signal when the low hanging air hose blocks the beam and prevents it from impinging on the receiver. These devices are typically installed at a fixed height(s) above the top of the rails and may have single or multiple laser transmitter/receiver pairs. The devices typically include a railroad car wheel detector and railroad car radio identification tag reader such that the interrupting air hose assemblies can be associated with the appropriate pair of coupled railroad cars. The railroad car wheel detector data is also used to locate the coupler gaps where low-hanging air hose assemblies are located as other components in the train, such as wheels and truck frames, also interrupt the laser beams.
U.S. Pat. No. 6,411,215 (2002) to Shnier discloses placing a retro-reflective surface on a target such as a door's locking handle. Then a narrow light beam is focused on the desired position of the retro-reflective surface. If a monitoring device does not sense the reflected light, then an alarm is activated. Unfortunately, the dirt and grime associated with railroad coupling and braking devices would defeat this approach for detecting a low air hose.
U.S. Pat. No. 6,717,514 (2004) to Stein et al. discloses a radio transmitter mounted to a target. A trio of spatially positioned receivers detect an alarm condition when the transmitter is located outside of a safe perimeter. Unfortunately, the installation and maintenance of countless radio transmitters on air hose elements would be costly and prone to failures of the radio transmitters.
U.S. Pat. No. 6,778,092 (2004) to Braune discloses a camera, laser or two cameras connected to an evaluating unit which determines (using software) location and time variables in a safety zone of a robotic machine installed in a factory. The machine can be shut down when predetermined danger conditions exist. This technique is somewhat similar to the present invention, except the logic needed to analyze a passing train is not suggested, nor are solutions to variable outside weather and light conditions suggested.
U.S. Pat. No. 6,812,850 (2004) to Matsuuiya et al. discloses a CCD camera moving in X, Y, Z axes to track a work piece. A protector on the camera includes an antenna and a strain detector, used to prevent a collision of the camera and the work piece.
Pub. No. US2002/0196155 to McNulty, Jr. discloses a fixed laser beam hitting a mirror on a target. A door opening moves the mirror, interrupting the reflected beam, and signaling an alarm.
Pub. No. US2003/0160701 to Nakamura et al. discloses a container contents proximity sensor with a wireless transmitter to detect a terrorist entry into a container.
Salient Systems, Inc. discloses a low hose detector using an optical sensor, a light curtain sensor, to examine the area between railroad cars. Car tag readers also log offending cars. A plurality of lasers are beamed across the track and sensed by receivers. By measuring the height of the lowest beam interrupted by the air hose, a low air hose is detected, as well as all heights of all passing air hoses to within an inch.
GE Transportation Rail® produces a dragging equipment detector that consists of a bar mounted across the tracks. The bar is height adjustable to detect a low air hose by sensing the impact with the bar.
Lynxrail™, www.lynxrail.com, produces a video imaging system for passing railroad cars. It monitors via machine vision algorithms wheel profiles, brake shoe wear, springs, car identification, hand brake and draft gear. No backlit screen or equivalent is known to be used to compensate for daytime, nighttime and ambient weather conditions.
The prior art has the following problems:
1. Proper alignment of the laser transmitter and receiver must be maintained at all times.
2. The laser beam devices must be mounted across and in close proximity to the track and are subjected to severe vibrations that can cause the laser beam to deflect from the receiver, especially when railroad car wheels with flat spots pound the rails.
3. The housings for the laser and receiver interfere with normal track maintenance activities and may pose a trip hazard to railroad workers.
4. The simple beam-break approach is very poor at discriminating shapes and sizes. Broken straps, cables, debris precipitation and other objects can block the laser beam and cause a signal change at the receiver, referred to as a “false positive.”
5. The prior art only detects low hanging air hose assemblies and cannot be used for other detection tasks.
The present invention compensates for all lighting conditions by providing a lit screen or other light uniform background, such as a building or wall, to backlight the space between passing railroad cars. A camera is used to detect a low air hose via machine vision algorithms. A car gap detector can be used to utilize a laser beam to sense when the gap between the cars is properly lined up with the video camera. A wheel counter can identify the car with a defectively low air hose. An image acquisition control computer can send an alarm to a remote location via the internet.
The invention described herein offers significant improvements over the prior art:
1. The imaging camera is located well off the track (27′ from track centerline) in a protective enclosure and is not subjected to vibrations.
2. Being located well off the track, the imaging camera does not interfere with normal track maintenance activities in any way or create a trip hazard to railroad workers.
3. The image analysis software contains sophisticated algorithms to discriminate against any object in the image that does not have the precise characteristic size and shape of an air hose. The analytical technique executed in the software is very proficient at avoiding false positive indications from broken straps, cables, debris, precipitation or other objects that may enter the field of view of the imaging camera.
4. The invention is also useful for measuring the railroad car coupler heights which are also located in the same “coupler gap” areas as the air hose assemblies.